Pneumatic Flanged Butterfly Valves

Spring-return (fail-safe): Returns to a safe position (open or closed) on air loss — the usual requirement for emergency shutdown (ESD) and for isolation where the valve must not stay open. Slightly larger cylinder and a lower output torque, so check the spring-stroke torque when sizing.
Double-acting: Needs air both ways; fails in place on air loss. More compact and economical, ideal for modulating/throttling service where fail-safe is not mandated.

Wafer: Sandwiched between two pipe flanges using through-bolts. Cheapest, lightest, but one side must stay bolted for maintenance. Best for non-critical, dead-end not needed.
Lug: Has threaded inserts (lugs) with independent bolts. One side can be disconnected while the valve stays sealed against the other flange — ideal for dead-end service, tanks, equipment isolation.
Flanged (double-flanged): Has its own integral flanges matching pipe flanges. Strongest, supports pipe loads, best for large sizes (DN300+), buried service, and high-vibration applications.

EPDM: Best all-round for water, air, and weak chemicals up to +120°C. Most common choice.
NBR (Buna-N): Good for oils, fuels, petroleum products, aliphatic hydrocarbons. Avoid with aromatic solvents and strong oxidizers.
Viton/FKM: Excellent for acids, aromatics, and high temperatures up to +200°C. Costlier but essential for chemical processing.
PTFE: Near-universal chemical resistance. Used for corrosive acids/bases. Lower temperature limit than rubber (cold-flow concern below 0°C).
Metal seat (SS316/Inconel/Stellite): Required for steam above +180°C, high-pressure gas, and services with abrasive particles that would embed in rubber seats.

Yes — within limits. Concentric rubber-lined valves modulate reasonably well in the 20°–70° open range and are commonly used for balancing in HVAC systems. However, for precise control or high ΔP service, double-offset or triple-offset valves with characterized discs give much better linearity, less torque variation, and longer seat life under cycling conditions.

Double-offset (High-Performance): The shaft is offset behind the disc centerline and also offset from the body centerline. This causes the disc to swing away from the seat immediately upon opening, reducing friction and wear. Good for higher pressure/temperature than concentric, up to ~+230°C.
Triple-offset: Adds a geometric conical seat shape as a third offset. The metal-seated disc contacts the seat only at the fully closed position with zero rubbing during opening/closing cycle. Enables metal-to-metal shutoff quoted to ISO 5208 in steam and high-temperature gas service up to +550°C, replacing gate and globe valves at a fraction of the weight and cost.

The actuator torque must exceed the valve's breakaway (opening) torque plus a safety factor of 1.3–1.5×. Key factors: valve size (larger = more torque), pressure differential (higher ΔP = more torque), seat material (rubber has more friction than metal), and whether it's spring-return (spring force adds to required torque). Send us your valve model, size, pressure rating, and fail-position preference — we'll specify the correct actuator package pre-mounted and tested.

Rubber-lined concentric valves are nearly maintenance-free for 10–15 years in clean water service. Periodic checks: inspect seat for wear/cracks, check disc/stem for corrosion, verify actuator torque. Lug and flanged types allow in-line seat replacement. For offset valves: check seals, re-torque body bolts if needed, and lubricate the gearbox (if equipped) annually. In dirty/slurry service, plan more frequent inspections.

From the valve's break torque and run torque, multiplied by a safety factor for the medium — about 1.25 for clean water, 1.5–2.0 for dry or abrasive media such as cement or calcium carbonate powder. For spring-return units the torque must be checked on the spring stroke as well, which is why a fail-safe actuator is often one frame size larger than the double-acting unit for the same valve. Send us the size, medium and air pressure and we will size it for you.

Filtered, dry air at 4–8 bar; most actuators are sized at around 5.5 bar. We supply a filter-regulator-lubricator unit with a gauge as standard so the pressure at the actuator is known. Lubricated air is not mandatory but extends seal life; if your plant supplies oil-free instrument air, tell us and we will select the seals accordingly.

Yes. The actuator, mounting kit, solenoid valve, limit switch box and FRL are assembled and function-tested on the valve before packing, and we can send the test record with the shipping documents. The valve and actuator interface is ISO 5211, so the actuator can be replaced in the field without machining.

The solenoid coil and switch box are supplied with the component manufacturer's declaration and IP rating datasheet, and we will confirm exactly what documentation can be provided for your area classification before you commit. We do not hold ATEX or IECEx certification in our own name, so for a classified area the certificate is the component maker's, not ours — please do not assume otherwise from a datasheet.